The present invention relates to a seat frame and a vehicle seat, and particularly to a seat frame and a vehicle seat that reduces an impactive shock that would otherwise be applied to a neck portion upon a rear-end collision.
Conventionally, upon so-called rear-end collision such as a collision against a rear portion of a vehicle, and collision of a vehicle during rearward movement thereof, it is likely that a head portion of a seating occupant is suddenly tilted rearward due to inertial movement such that a neck portion of the occupant is likely to be subjected to an impactive shock.
Thus, seats for vehicles such as automobiles are each provided with a headrest located above a seat-back and configured to receive a head portion of an occupant from the rearward, so as to protect the head portion, a neck portion, and the like of the occupant and to mitigate an impact against the head portion upon rear-end collision.
However, even with the provision of the headrest, it is sometimes impossible to sufficiently mitigate an impactive shock that is otherwise applied to the neck portion of the occupant, in case of an excessive impact energy upon rear-end collision so that the head portion of the occupant is subjected to an increased impact from the headrest.
To solve such a problem, there has been proposed a technique configured to apply a resistance force from an impact absorbing element that is produced by successive and stepwise breaking deformations of impact absorbing holes with an engagement pin, to a seat-back frame, upon rearward tilting of the seat-back frame relative to a rotational arm, thereby enabling absorption of impact energy upon rear collision (see Japanese unexamined patent publication no. 1998-278644 (“the '644 Publication”), for example).
Further, there has been proposed another technique configured such that a front portion and a rear portion of a substantially rectangular connecting member formed of a material such as soft iron having a larger deformation resistance are attached to a front portion of a rail of a seat leg portion and to a vehicular body floor around the seat leg portion, respectively, while providing a rotational hinge portion at a rear end portion of the rail, in a manner to absorb an impact energy upon rear-end collision via deformation of the connecting member (see Great Britain patent document no. GB2359482A (“the '482 Publication”), for example).
However, according to the technique proposed by the '644 Publication, absorption of impact is intermittently conducted upon breakage of partitions among impact absorbing holes, thereby problematically failing to attain a remarkable impact mitigating effect.
Further, in case of the configuration proposed by the '482 Publication, it is impossible to absorb an impact upon exceeding an extent of deformation of the connecting member, thereby problematically failing to sufficiently absorb a strong impact.